[Merged by Bors] - Fixed #1768

boa/src/syntax/parser/cursor/buffered_lexer/mod.rs

@@ -17,12 +17,12 @@ const MAX_PEEK_SKIP: usize = 3;
 /// The fixed size of the buffer used for storing values that are peeked ahead.
 ///
 /// The size is calculated for a worst case scenario, where we want to peek `MAX_PEEK_SKIP` tokens
-/// skipping line terminators:
+/// skipping line terminators, and the stream ends just after:
 /// ```text
-/// [\n, B, \n, C, \n, D, \n, E, \n, F]
-/// 0 0 1 1 2 2 3 3 4 4
+/// [\n, B, \n, C, \n, D, \n, E, \n, F, None]
+/// 0 0 1 1 2 2 3 3 4 4 5
 /// ```
-const PEEK_BUF_SIZE: usize = (MAX_PEEK_SKIP + 1) * 2;
+const PEEK_BUF_SIZE: usize = (MAX_PEEK_SKIP + 1) * 2 + 1;
 
 #[derive(Debug)]
 pub(super) struct BufferedLexer<R> {
@@ -49,6 +49,7 @@ where
  None::<Token>,
  None::<Token>,
  None::<Token>,
+ None::<Token>,
  ],
  read_index: 0,
  write_index: 0,

boa/src/syntax/parser/cursor/buffered_lexer/tests.rs

@@ -278,3 +278,11 @@ fn skip_peeked_terminators() {
  // End of stream
  assert!(cur.peek(2, true, &mut interner).unwrap().is_none());
 }
+
+#[test]
+fn issue_1768() {
+ let mut cur = BufferedLexer::from(&b"\n(\nx\n)\n"[..]);
+ let mut interner = Interner::default();
+
+ assert!(cur.peek(3, true, &mut interner).unwrap().is_none());
+}

boa/src/syntax/parser/expression/assignment/mod.rs

@@ -153,8 +153,9 @@ where
  .map(Node::ArrowFunctionDecl);
  }
  TokenKind::Punctuator(Punctuator::CloseParen) => {
- // Need to check if the token after the close paren is an arrow, if so then this is an ArrowFunction
- // otherwise it is an expression of the form (b).
+ // Need to check if the token after the close paren is an
+ // arrow, if so then this is an ArrowFunction otherwise it
+ // is an expression of the form (b).
  if let Some(t) = cursor.peek(3, interner)? {
  if t.kind() == &TokenKind::Punctuator(Punctuator::Arrow)
  {